Ehrlich and raven hypothesized that if a new defensive trait evolves in a single plant species (or if a new trait to counteract a plant's defenses evolves in an herbivore species) the appearance of that trait could result in a period of species diversification. their hypothesis is also referred to as the hypothesis.

Coevolution

Explanation:

Ehrlich and Raven observed butterfly species and their host plants. Plant species had adopted a series of defence mechanisms against butterflies. In response the butterflies also evolved new traits to avoid these defence mechanisms.

In this way both butterflies and plants influenced each other's traits and they co evolved. The coevolution can lead to accumulation of lot of different characteristics which can lead to formation of new species and species diversification. Formation of new species will be observed both in plants and butterflies.

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